Vocal Cord Paralysis and Feeding Difficulties as Early Diagnostic Clues of Congenital Myasthenic Syndrome with Neonatal Onset: A Case Report and Review of Literature

Herein, we present a newborn female with congenital vocal cord paralysis who required a tracheostomy in the neonatal period. She also presented with feeding difficulties. She was later diagnosed with a clinical picture of congenital myasthenia, associated with three variants of the MUSK gene: the 27-month follow-up was described. In particular, the c.565C>T variant is novel and has never been described in the literature; it causes the insertion of a premature stop codon (p.Arg189Ter) likely leading to a consequent formation of a truncated nonfunctioning protein. We also systematically collected and summarized information on patients' characteristics of previous cases of congenital myasthenia with neonatal onset reported in the literature to date, and we compared them to our case. The literature reported 155 neonatal cases before our case, from 1980 to March 2022. Of 156 neonates with CMS, nine (5.8%) had vocal cord paralysis, whereas 111 (71.2%) had feeding difficulties. Ocular features were evident in 99 infants (63.5%), whereas facial-bulbar symptoms were found in 115 infants (73.7%). In one hundred sixteen infants (74.4%), limbs were involved. Respiratory problems were displayed by 97 infants (62.2%). The combination of congenital stridor, particularly in the presence of an apparently idiopathic bilateral vocal cord paralysis, and poor coordination between sucking and swallowing may indicate an underlying congenital myasthenic syndrome (CMS). Therefore, we suggest testing infants with vocal cord paralysis and feeding difficulties for MUSK and related genes to avoid a late diagnosis of CMS and improve outcomes.

Case Report: Congenital Myasthenic Syndrome Presenting with Bilateral Vocal Cord Paralysis Caused by De-Novel Compound Heterozygous MUSK Mutation

Background

We report the genetic etiology of a case of bilateral vocal cord paralysis in a female infant.

Case Description

The female infant developed dyspnea after birth, which improved with treatment, allowing her to be discharged from the local hospital. At 2 months of age, the child experienced a recurrence of dyspnea and was treated in a local hospital with interventions such as tracheal intubation and mechanical ventilation. However, as the child continued to suffer from dyspnea, she was transferred to the neonatal intensive care unit of the Children's Hospital affiliated to Zhengzhou University for further treatment. A second electronic nasopharyngoscopy examination revealed bilateral vocal cord paralysis. The child underwent a tracheostomy due to a failure to wean from mechanical ventilation; after surgery, the respirator was effectively removed, and oxygen delivery ceased. The child and her parents underwent genetic testing with next-generation sequencing technology, which revealed that the child had two heterozygous variants in the MUSK gene, namely the c.2287G>A heterozygous mutation (p.Ala763Thr) and the c.790C>T heterozygous mutation. In addition, Sanger sequencing was performed, which confirmed that these two mutations were, respectively, inherited from the mother and father.

Conclusion

Congenital myasthenic syndrome caused by MUSK gene mutations can present clinically as bilateral vocal cord paralysis in neonates.